Recent advances in biochemistry and immunology now make possible new approaches for detection and treatment of infectious diseases. Our group is committed to such technological applications, and this Phase I proposal is in response to the stated interest of the N.I.A.D.A. in such innovative biomedical technologies. Specifically, this application describes our interest in developing a monoclonal antibody based immunoassay for the E.coli heat stable enter toxin (ST), which causes 'traveler's diarrhea' in humans, and wide spread often fatal infectious diarrhea (scours) in newborn livestock. Our two Phase I goals will be 1. to generate a panel of murine monoclonal antibodies to the toxin, and 2. to commence development of a sensitive and versatile ST fluorescence immunoassay. Purified monoclonal antibocies will be conjugated to B-galactosidase and tested in a heterogeneous competitive assay format. We intend to pursue solid-phase methods for immobilization of ST-albumin conjugates, which will then compete the test sample fcr binding to antibody-enzyme conjugates. Enzyme activity (and subsequently, ST concentrations) will be measured in a fluorescence assay, monitoring the formation of methyl-umbelliferone from the non-fluorescent substrate, methyl-umbelliferyl galactoside. The final (fluorescence) measurements can be made in any appropriately set fluorimeter, or in a low-cost, portable photon-counting fluorimeter which we have been developing for use with such immunoassays. Both the instrument and the assay format are geared towards rapid, technically facile performance in a laboratory or 'field' setting. Due to the health and economic impact of toxin related diseases, we believe there are significant human and veterinary commercial markets for such a toxin detection method, as well as the possible commercial utility of such antibodies as therapeutic agents. Our group is also well positioned to attract follow-on funding for this project and to develop/market such commercial products. The technology developed should also be applicable to other infectious diseases and to the long term objectives of N.I.A.I.D. research program.